A new biography exposes the mysterious confidence behind George W. Bush’s greatest failures.

Jean Edward Smith’s biography of George W. Bush goes on sale a day before the former President’s seventieth birthday, and it’s safe to say that no one will be bringing it as a present to the ranch outside Crawford. Smith, a well-regarded practitioner of military history and Presidential-life writing, comes straight to the point in the first sentence of his preface: “Rarely in the history of the United States has the nation been so ill-served as during the presidency of George W. Bush.” By the book’s last sentence, Smith is predicting a long debate over whether Bush “was the worst president in American history,” and while the biographer doesn’t vote on the question himself, the unhappy shade of James Buchanan will feel strongly encouraged by his more than six hundred pages.

And yet, for all the overheated denunciations—a rhetorical comparison gets made between Bush and Hitler—“Bush” (Simon & Schuster) doesn’t feel like a hatchet job. Like Bush himself, it is susceptible to sudden changes of heart and tone, and it never quite gets over a sense of loss for aspects of the pre-9/11 figure that Smith seems to enjoy imagining, however sketchily, in the book’s early stages.

The writer certainly doesn’t revile the compassionately conservative candidate of 2000. Bush may have permitted some brutal staff maneuvers against John McCain, but the campaign that Smith re-creates is mostly distinguished for eschewing “Nixon’s classic formula of running to the right in the primaries and then moving back to the center for the general election.” Making plans to govern “as the nation’s C.E.O.,” Bush disavowed nation-building abroad and put forward an agenda almost entirely focussed on what no one yet called the homeland. By Smith’s reckoning, Bush ran a better campaign, and then a better recount, than his opponent. If the author favors the dissent in Bush v. Gore, he never questions Bush’s legitimacy or lets up on the unappetizing aspects of his opponent, from Gore’s inclination toward “résumé enhancement” to his pompous debating demeanor. (Four years later, in his first duel with John Kerry, a charmless, impatient Bush seemed almost fatefully infected with a variant of Gore’s earlier boorishness.)

Smith points out that Bush attended no meetings of the National Security Council in the seven months prior to September 11, 2001. In her reports on these gatherings, Condoleezza Rice—Bush’s national-security adviser, workout partner, and something of an alter ego—tended to synthesize disagreements among the participants, leaving Bush with a false feeling of consensus. The President’s own focus was chiefly on matters like stem-cell-research regulation and the sort of educational reforms he had pushed through a Democratic legislature as governor of Texas. On the morning of 9/11, Laura Bush was in Ted Kennedy’s Senate office, having come to testify for the No Child Left Behind Act; the White House she returned to later that day was a wholly different place, a domestic cruise ship that had become an aircraft carrier.

In Smith’s view, the military and moral calamities began right then. If he is moderately critical of the President for being “asleep at the switch” in the period before the terrorist attacks—Bush felt no particular alarm when an August 6th C.I.A. briefing indicated that Osama bin Laden was up to at least something—the biographer is simply aghast once Bush seizes the controls. Within three days of September 11th, he says, the President had acquired a “boundless” confidence that put the country on a “permanent war footing” and the White House into a “hothouse climate of the President’s certitude.”

The war in Afghanistan, whose necessity Barack Obama insisted on in 2008 and beyond, is deemed by Smith to be scarcely more justifiable than the later one in Iraq: both are “disastrous wars of aggression.” In an earlier book, Smith found the Gulf War fought under George H. W. Bush to be uncalled for as well, and here he seems comfortable making a distinction that holds the September 11th attacks to have been “tragic, but scarcely catastrophic.” The younger Bush’s with-us-or-against-us assertion in his September 20, 2001, speech to Congress (“Any nation that continues to harbor or support terrorism will be regarded by the United States as a hostile regime”) was in some respects only an amplification of what Bill Clinton had stated three years before (“Countries that persistently host terrorists have no right to be safe havens”), but Smith reads it as “a serious overstatement.” Maybe so, but his chapter “Toppling the Taliban” might have more revisionist force if it weren’t deployed with so many overstatements of its own: “Within a month [of September 11th], the United States had lost world sympathy.”

In another anti-superlative, Smith suspects that the invasion of Iraq will “likely go down in history as the worst foreign policy decision ever made by an American president.” The thirteen-year legacy of “preëmption” makes this a hard prophecy to counter, and Smith’s well-ordered scenes on the subject—Paul Wolfowitz pushing for war against Saddam on September 12th, just as he’d been pushing for it in April—do dismaying work. James Baker and Brent Scowcroft, the wise men of his father’s Administration, tell Bush to go slowly or not at all, but George Tenet, the holdover C.I.A. director from the Clinton years, assures him that convincing the public of the need to invade Iraq over W.M.D.s will be a “slam dunk.” As persuasively as anyone before him, Smith presents a strong story of how a successful military mission quickly unaccomplished itself; turned into quite something else (“the United States was going to bring democracy to the country”); and then festered into what Donald Rumsfeld himself, in his memoirs, judged to be “a long and heavy-handed occupation.”

The dark thread of Smith’s book is what he calls the “torture trail” of rendition and enhanced interrogation and prisoner abuse, a pathway perhaps made inevitable when Bush, after 9/11, “elevated the terrorists to the status of belligerents” but not combatants. Smith pays devastating attention to how the military figures around the President argued strenuously against behaviors that could be construed as violations of the Geneva Conventions. Generals Tommy Franks and Richard Myers, along with Secretary of State and retired General Colin Powell, insisted that, regardless of the casuistic memos coming out of the Justice Department’s Office of Legal Counsel, any skirting of international law put American fighters at a retaliatory risk of the same treatment. In 2005, John McCain, who had been brutalized by his North Vietnamese captors four decades earlier, shepherded an “anti-torture amendment” through Congress over the Administration’s energetic opposition; after an apparent reconciliation, Bush insulted McCain not with a veto but with a signing statement that made clear he would interpret the amendment however he liked. Military men—Grant, Eisenhower, General Lucius Clay—have often served as Smith’s subjects, and his scorn for the modern-day civilian “chicken hawks” is so strong that he chooses this quotation from General H. Norman Schwarzkopf for a chapter epigraph: “After Vietnam we had a whole cottage industry develop, centered in Washington, D.C., that consisted of a bunch of military fairies that had never been shot at in anger.”

It may have been Vice-President Dick Cheney who first advocated military commissions instead of civilian trials for captured terrorists, and it may have been the N.S.A. director Michael Hayden who urged going to “the edge,” but each step through this dank basement resulted not from “decisions made by Cheney, Tenet, Rumsfeld, or the military. They were direct decisions of the president.” Bush relished the speed with which he made them, and gave himself the title of the Decider. Smith’s post-9/11 Bush is both doubt-free and indubitable, a man who effected the “personalization of the war on terror” and of Presidential power in general.

But where is the personality of this personalizer? How does a man whom Smith scarcely describes come to work such a mighty will over appointee after appointee and agency after agency? Where, in short, is the Bush in “Bush”?

Smith may have the Carlylean sense that history is shaped more by the decisions of individuals than by the large movements of social forces, but he is fundamentally more a historian than he is a biographer, and much more comfortable when his current subject is holding a meeting in the Roosevelt Room than when he is riding his off-road Trek bicycle. The author’s disinclination toward the private and the psychological leaves a reader of “Bush” wondering exactly when and how an “unnerving level of certitude” took hold of the title figure. If no President “since Woodrow Wilson has . . . so firmly believed that he was the instrument of God’s will,” just how did the messianic annunciation take place? Smith says that, shortly after 9/11, James Merritt, once president of the Southern Baptist Convention, told Bush, “God knew that you would be sitting in that chair before the world was ever created.” But lots of pastors tell lots of Presidents lots of things, and most devout Christians believe what Merritt said about whatever chair they sit in.

After covering the failure to find W.M.D.s in Iraq, Smith compares the President to Captain Queeg for displaying “a willfulness that borders on psychosis.” If Bush is going to earn the comparison, his biographer needs to do a better job of demonstrating how he travelled what would have been a long road from the mind-set of his days at Harvard Business School: there, Smith says, he was merely “energetic, but ill-informed, untutored, and unread.” Both of these purported Bushes are observed by Smith from an abstract and considerable distance, the biographical equivalent of Bush’s aerial assessment of Hurricane Katrina, and Smith approaches the earliest parts of the life with no more sustained attention than Bush himself approached Yale. The future President has reached the age of thirty-one—back in his childhood home of Midland, Texas, ready to make a losing run for Congress—by page 29.

Smith is not the first student of Bush to realize that he is more his mother’s son than his father’s, but readers of “Bush” don’t get to see the forging of the bond. Robin Bush, George W.’s younger sister, who died of leukemia at the age of three, comes and goes in a phrase. One has to turn to something like Pamela Kilian’s modest biography of Barbara Bush, from 1992, to learn that not long after her daughter’s death Mrs. Bush “overheard George tell a friend, ‘I can’t play today because I have to be with my mother—she’s so unhappy.’ ” He was learning to be not an overachiever but entertaining. There are still people around who can flesh out such events, but it seems that awfully few original interviews have gone into “Bush”; the book is widely but secondarily sourced, and in places could more rigorously attribute direct quotations. Bush himself did not sit down with the author.

At the bottom of Smith’s pages, one finds a great many extended, conversational footnotes. Often they are historical asides, interesting if somewhat tangential, but so numerous as to form a kind of retreat, a typographical Camp David where author and reader keep avoiding the heart of the biographical matter. One is left wondering about so many things. What Bush gained by giving up drinking—a fast, if late, career start; the chance to be a more responsible husband and father—is indisputable; but did he lose anything? Some antic part of himself, the one that once cheered a grief-stricken mother? Most important, if Bush’s faith gave him certainties that became overweening and dangerous during his Presidency, why did they not so manifest themselves while he was on the road to Damascus fifteen years earlier, or when he was inveighing against nation-building in 2000? Smith gives us a few interesting details about upstairs life in the White House during the weeks after 9/11 (the President and Laura Bush both began taking Cipro after the anthrax letters arrived at the Capitol), but it remains the work of another biography to show whatever inner transformation Smith believes occurred during that “tragic, but scarcely catastrophic” period.

Bush himself was a consumer of biography, from Marquis James’s “The Raven,” a study of the redeemed alcoholic Sam Houston, to the fourteen lives of Lincoln that he read during his eight years in the White House. Smith is aware of all this, but seems not to believe that point of view belongs to biography and not just the novel. In episode after episode of this volume, one wishes for a sustained attempt—however qualified and speculative—to imagine what Bush himself might really have been thinking, beyond the face-value quotations from his own and others’ memoirs. During the recount, was his sense of mental well-being intact or hanging like a chad? What about that walloping facial boil he developed? It was an eruption famous enough to inspire an episode of “Veep,” but it goes unmentioned in “Bush.” Smith’s book ultimately has less intimacy than such as-it-happened histories of the Administration as Peter Baker’s “Days of Fire.”

Smith’s prior works, to which he frequently refers, supply odd, handy moments of precedent and perspective. When we hear Bush arguing that John Roberts’s sunny, consensus-building temperament is an important qualification for a Chief Justice, Smith, the author of “John Marshall: Definer of a Nation,” reminds the reader that the “charm and easy manner” of Roberts’s distant predecessor may have been even more important than his intellect. In pointing out that Bush served as head cheerleader at his prep school, he notes that this “was something of a leadership position at Andover”—phrasing that the reader takes for sarcasm until Smith goes on to explain, in earnest, that Eisenhower and Reagan held the same post at West Point and Eureka College, respectively.

But history doesn’t supply psychology, and perspective is not the same as perspicacity. Smith quotes, without disagreement, Barack Obama’s courteous but manifestly untrue remark that Bush is “comfortable in his own skin.” Those who observed the President’s sudden shifts from the guy “you wanted to have a beer with” to stinging scold have realized that they were experiencing not so much changes in mood as moment-by-moment veerings between different selves, each authentic but neither integrated to any normal extent with the other. Bush’s fanatical insistence on punctuality and his ever more exacting physical-fitness routines seem less a matter of self-discipline than of self-control, which is something different and more desperate. His habitually early bedtime may have derived from how exhausting he found it to be himself.

The years 2005 and 2006 were Bush’s anni horribiles, the period that included the worst of the insurgency in Iraq, Hurricane Katrina, and an off-year electoral “thumping”—Bush’s word—that turned both houses of Congress over to the Democrats. (Full, defensive disclosure: I served during some of this period as deputy chairman of the National Endowment for the Humanities, where, “Brownie” aside, we did a heckuva job getting small emergency grants to cultural institutions on the Gulf Coast.) But the second term began with Bush playing offense on all fronts: his Inaugural Address on January 20, 2005, proclaimed it to be “the policy of the United States to seek and support the growth of democratic movements and institutions in every nation and culture, with the ultimate goal of ending tyranny in our world.” Two weeks later, he gave a State of the Union address that returned the emphasis to domestic initiatives that he had had to defer since September, 2001: he intended to transform Social Security through private retirement accounts, and he would liberalize immigration policy. “Family values don’t stop at the Rio Grande,” he had liked saying in 2000, the sentiment an oratorical forerunner to his brother Jeb’s characterization of the “act of love” that motivates people to cross the border.

“Bush was reaching for the stars,” Smith writes. “His foreign policy aim was to spread democracy throughout the world, his domestic goal was to enshrine individual choice. The common denominator was personal liberty.” Having won the second term his father lost, he had the “vision thing” that his father didn’t, and Smith is aware of it. The author could have made Bush’s international AIDS initiative, which ultimately directed tens of billions of dollars abroad, into a grudging footnote, but he instead gives a full chapter to what he calls “an amazing achievement,” perhaps the most lasting one of the Bush Presidency.

Immigration and Social Security, however, came to naught, in large measure because of Hurricane Katrina. “Politically, [Bush] could never recover” from his slowness off the mark, Smith says; his perceived indifference hurt him more in the second term than the perception of illegitimacy had hobbled him in the first. He could not have been unaware that his Presidency was floating away, and that Iraq appeared ready to end not in a muddle but in a rout. Smith quotes Karen Hughes, one of the “Iron Triangle” of aides Bush brought with him from Texas to the White House in 2001: “He felt really strongly that it was his sheer force of will that was holding the line between winning and losing the war. That everybody else was ready to abandon it.” Bush had to persuade Rice, who had become the Secretary of State, to overcome her doubts about the five-brigade “surge” that eventually reversed the slide. In ordering the change, he told the skeptical Joint Chiefs of Staff, “I am the President”—a reminder that they had been out of the chain of command since 1986. The surge seems to be the only military decision by Bush that Smith half approves of, via a kind of mathematical paradox: “The fact that the surge was not solely responsible for the decline in violence in Iraq in no way diminishes its importance. By coinciding with the decline it provided Bush with a rationale for beginning the drawdown of American forces.”

Iraq’s greater stability probably allowed Bush to get through the 2008 financial crisis as well as he did. Smith faults him for a slow, Katrina-style response to the subprime-mortgage collapse, but sees him taking command in time to push the TARP bill through Congress on its second try: “If we’re really looking at another Great Depression,” he said, “you can be damn sure I’m going to be Roosevelt, not Hoover.” He was by now “very much alone” in a White House devoid of stalwarts and familiar faces; the relationship with Cheney, even before their falling out over the President’s refusal to pardon I. Lewis (Scooter) Libby for his part in the Valerie Plame affair, wasn’t what it used to be. Smith, offering a supreme irony, or maybe just a supreme concession, says that Bush, albeit ferociously unpopular, was at last, in 2008, “growing into the job.”

George W. Bush was absent from the 2008 Republican Convention, to the pleasure of his would-be successor, John McCain, who experienced a moment of luck in the form of Gustav, another hurricane. The Republicans cancelled the Convention session for which Bush’s and Cheney’s in-person appearances were scheduled; the assemblage in St. Paul, Minnesota, was hardly threatened by the storm, but McCain took the opportunity to show the voters how quick­­ly he could get down to the Gulf Coast.

Three weeks from now, Bush will once more be absent, as the Republicans convene in Cleveland to nominate the man who steamrolled the former President’s “low-energy” brother. One strength of Smith’s biography is the way it makes the reader continually consider whether the foreign overreachings of the forty-third President will prove more lastingly harmful to the country and to the world than the underreachings of the forty-fourth, but that is not a matter that will be on the Republicans’ mind this July. They will be gathering for a political Jonestown, pledging to help elect as the next Commander-in-Chief a man who insists that a protester who rushed the platform from which he spoke last March had “ties to ISIS.” (He knows because it was “on the Internet.”) Bush will perhaps be at his Crawford ranch, maybe even painting one of his odd, Hockneyesque canvases. They glow not with faraway fires or any particular certitude, just a sort of opaque serenity, something that may at last have descended on a man no longer obligated to see past the fence. ♦

This article appears in other versions of the July 4, 2016, issue, with the headline “W Is for Why.”

Thomas Mallon, a novelist, an essayist, and a critic, is the author of, most recently, “Finale: A Novel of the Reagan Years.”